The use of equipment including industrial processors requiring relatively high currents is becoming increasingly common. In the powering of such equipment, it is considered unsafe to allow a switch to be moved to the "on" position in the absence of a properly inserted plug. Attempting to insert or remove a plug from an energized receptacle, especially with a load connected to the plug, can result in arcing between the plug and receptacle with damage to the components as well as creating a substantially safety hazard to personnel. To prevent this occurrence, switches are often enclosed within a housing and commonly provided with some type of interlock mechanism.
These switch enclosures are often employed in environments requiring certain sanitary conditions such as food processing stations. To maintain the sterility of the food processing environment, the entire system must be periodically cleaned. In the cleaning process, the switch houses are subjected to substantial water pressure. However, the water pressure is not uniformly distributed about the housing and may often impact only parts of the housing. Therefore, if there are any recesses, or grooves in the housing, these may tend to accumulate matter and reduce the effective cleaning. Face mounted switch operating handles are particularly exposed to the environment and the cleaning process and may provide access for fluid penetration of the housing.
U.S. Pat. No. 5,298,701 to Sandor, discloses a high current switch operator mounted in a closed housing having a switch and a receptacle, wherein the housing includes an interlock mechanism to prevent operation of the switch to the ON position unless a plug is properly inserted in the receptacle. A face mounted handle is attached to a shaft which directly turns a gear (designated the second gear) which carries the interlocking components.
The Sandor interlocking components include a stepped recess in the second gear and a latch for engaging the recess when the handle is in the OFF position, a second recess in the second gear adjacent the first recess captures the latch and prevents further movement of the handle when the plug is not fully inserted. A first gear of equal size is coupled to the second gear and operates the switch when the handle is moved and a third gear is interposed between the first and second gears for ensuring concurrent rotation of the switch and the handle. In such a system of gears the handle directly turns the second gear that carries the recess, which recess rotates in synchronism with the handle, and since the first gear also rotates in synchronism with the handle the amount of force applied to the gears is the same and limited to that needed to rotate the switch.